Have you tried the MTN Collect SMS? It is basically MTN's version of Call Collect.
With the new MTN Collect SMS, you can now stay in touch no matter what. This service allows MTN customers with low airtime, or those who do not want to pay for sending a particular text message, to send an SMS to another MTN customer free of charge. The receiver however, must accept charges for the inbound message.
The service thus affords an MTN customer (the recipient) to bear the cost of an incoming SMS from another MTN customer (e.g. family, child, employee, friend etc.).
Please note that if Customer B (Sponsor) declines paying for the Collect SMS message (A will receive a message saying B has declined paying) or if B texts any other response aside from Yes, Y, No or N (B subscriber will receive a message that he sent an unrecognized command), s/he will not be charged for Collect SMS, and the text message from Customer A will not be delivered.
Simply send your SMS to 38701 followed by the receivers phone number e.g 38701080312348678